In the offshore oil and gas industry and in similar technologies it is common to provide tubular members of various kinds extending down into the sea bed. An underwater structure is often provided, for example, on the seabed for restraining and/or guiding movement of the tubular member. Such arrangements may apply in a wide variety of circumstances and in some of those circumstances the structure is desired to restrain the tubular member passing through it from radial movement relative to the structure. Typically in the offshore industry, the forces which the restraint is required to resist are very high and conventionally such forces are provided by hydraulic systems. It is possible to devise a very simple hydraulic system for providing such radial restraint and for accommodating a very substantial radial force. For example pads may be pressed radially inwardly against a tubular member by respective hydraulic piston and cylinder arrangements with the pressure of the hydraulic fluid controlled to control the radial force. A difficulty with such an approach is that the reliability of a hydraulic system is most likely to become an issue over time and some maintenance of a hydraulic system is most likely to be required. That maintenance is expensive when the system is in an underwater environment.
The present invention seeks to mitigate the above-mentioned problem.